Select saute setting on a 6-qt. electric pressure cooker and adjust for medium heat.
Add half the ground beef, salt and pepper.
Cook and stir until no longer pink, 6-8 minutes; crumble beef.
Remove meat; drain any liquid from pressure cooker.
Repeat with remaining ground beef, salt and pepper.
Add butter, mushrooms and onions to pressure cooker; saute until onions are tender and mushrooms have released their liquid and are beginning to brown, 6-8 minutes.
Add garlic; cook 1 minute longer.
Return meat to cooker; add tomato paste and consomme. Press cancel.
Lock lid; close pressure-release valve. Adjust to pressure-cook on high for 5 minutes. Quick-release pressure.
Select saute setting and adjust for low heat.
In a small bowl, whisk together flour and water.
Pour over meat mixture; stir to combine.
Cook and stir until thickened.
Stir in sour cream; cook until heated through.
If desired, serve with noodles and minced parsley.